The subject matter described herein relates to semiconductor devices, such as photodiodes and photosensors.
Some known imaging systems include photosensitive detectors that receive incident radiation, such x-rays, to generate an image. The radiation is received by photodiodes in the detector and is converted into an electric charge or signal. The magnitude of the charge or signal can represent the amount of attenuation of the incident radiation and be used to generate an image.
In order to provide images with relatively high resolution, the photodiodes in the detector may need to be positioned relatively close to each other. The photodiodes can generate electrical signals that are not representative of the radiation received by the individual photodiodes. These signals are referred to as electrical crosstalk. The crosstalk can drift through the photodiode array in the form of electrons and electron holes (e.g., the absence of electrons at lattice points in the semiconductor structure of a detector). The crosstalk may drift from one cell of a photodiode array to another nearby cell within the same photodiode array and alter the charge or signal generated by the photodiode in response to receiving incident radiation. As a result, the image generated by the photodiodes may be negatively impacted by the crosstalk.
Some detectors include areas of a semiconductor substrate that are heavily doped with n+ dopants, such as phosphorus (P), in order to make the substrate more conductive. These areas attempt to prevent crosstalk from drifting between cells of the photodiode array by conducting the electrons of the crosstalk out of the photodiode array. However, the use of n+ doped regions can reduce the amount of crosstalk that is removed from the detector. For example, the n+ doped regions may reflect part of the crosstalk, such as the electron holes of the crosstalk, back toward the photodiode cells instead of conducting the electron holes out of the detector. As a result, at least some of the crosstalk may continue to drift to the photodiodes and degrade image quality.